Sinkhole risk in Shasta County, CA: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 9%
At or near the surface: 9%
Buried under cover: 0%

The next step for one property

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 340 of Shasta County's 3,776 square miles on soluble rock, 340 of them with the rock at or near the surface. With about 181,121 residents (48 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 268 map points about 3.8 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Shasta County

The nearest county rated sinkhole country is Emery County, UT, about 612 miles east. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Tehama County, CA 45 mi south · 1% at surface
Trinity County, CA 57 mi west · 25% at surface
Siskiyou County, CA 63 mi northwest · 9% at surface
Lassen County, CA 75 mi east · 0% at surface
Butte County, CA 79 mi south · under 1% at surface
Glenn County, CA 82 mi south · 0% at surface

What Shasta County is built on

The largest mapped soluble unit here is the Triassic marine rocks, unit 2 (Eastern Klamath Mountains) (mudstone), Middle to Late Triassic in age, covering about 8% of the county. Next is the Paleozoic marine rocks, undivided, unit 9 (Western Klamath Mountains) at 2%.

Against the rest of California

Shasta County ranks 4 of 58 in California for soluble rock at the surface, and sits above 67% of US counties on that measure.